1. Field of the Invention
The present invention relates to an optical plate for use in, for example, a backlight module, the backlight module typically being employed in a liquid crystal display (LCD).
2. Discussion of the Related Art
The lightness and slimness of LCD panels make them suitable for use in a wide variety of electronic devices such as personal digital assistants (PDAs), mobile phones, portable personal computers, and other electronic appliances. Liquid crystal is a substance that does not itself emit light. Rather, the liquid crystal relies on receiving light from a light source in order to display data and images. In the case of a typical LCD panel, a backlight module powered by electricity supplies the needed light.
FIG. 10 is a side cross-sectional view of a typical direct type backlight module 10 employing a typical optical diffusion plate. The backlight module 10 includes a housing 11, a plurality of lamps 12 disposed on a base of the housing 11, and a light diffusion plate 13 and a prism sheet 15 stacked on top of the housing 11 in that order. Inside walls of the housing 11 are configured for reflecting light toward the light diffusion plate 13. The light diffusion plate 13 includes a plurality of diffusion particles therein. The diffusion particles are configured for scattering the light, and thereby enhancing the uniformity of light output from the light diffusion plate 13. By scattering the light, the light diffusion plate 13 can correct what might otherwise be a narrow viewing angle experienced by a user of a corresponding LCD panel. The prism sheet 15 includes a plurality of V-shaped structures at a top thereof.
In use, light projecting from the lamps 12 enters the prism sheet 15 after being scattered by the light diffusion plate 13. The light is refracted and concentrated by the V-shaped structures of the prism sheet 15 so as to increase brightness of light illumination, and the light finally propagates into an LCD panel (not shown) disposed above the prism sheet 15. Although the brightness may be improved by the V-shaped structures, the viewing angle may be narrowed. In addition, even though the light diffusion plate 13 and the prism sheet 15 abut each other, a plurality of air pockets still exists at the boundary between them. When the backlight module 10 is in use, light passes through the air pockets, and some of the light undergoes total reflection at the air pockets. As a result, a light energy utilization ratio of the backlight module 10 is reduced.
Therefore, a new optical means is desired in order to overcome the above-described shortcomings.